Solid state lighting, in particular, light emitting diodes (LEDs), due to long service life, environmental friendliness and high efficiency, has became a new generation of lighting sources in replace of fluorescent lamps/incandescent bulbs. However, directly-fabricated LEDs only emit monochromatic light and require mixture of several colors to obtain white light. At present, to produce white light LEDs, blue/ultra violet LEDs are used to activate light conversion materials, like fluorescent powder.
In most LEDs, electrodes are made of highly conductive materials like Au, which will absorb some light. Therefore, electrode light absorption greatly reduces light emitting efficiency. In white light chips of the prior art as shown in FIG. 1, an electrode 105 mainly absorbs: 1) the light r1 from the light emitting layer 103 to the electrode bottom; 2) the light r2 from the light emitting layer 103 to the electrode sides; and 3) the light r3 scattered/excited from the light conversion material 107, like fluorescent powder, to the electrode top surface and sides.
To solve electrode light absorption, LED reflective electrodes in the prior art are divided into two types: 1) the electrode bottom is a reflector and its sides and top surface are still made of light-absorption metal. For LED chips with such electrodes, in particular, for white light chips, the light emitting efficiency is still reduced due to electrode light absorption; 2) the entire electrode is wrapped by reflective metal. However, the reflective metal, in general, Ag/Al, may cause electrode degradation due to metal electromigration during usage of LED chips.